After laying out what may be the boldest restatement of US national security strategy in half a century, the Bush administration is pressing forward to implement it in the high-profile case of Iraq.

The United States has been the world's only superpower at least since the fall of the Berlin Wall, but defining what that might mean, in terms of America's role in the world, has been taking shape more slowly.

The Bush administration's first National Security Strategy, released Friday, takes an unprecedented step away from cold-war views to confront a world beset by the likes of Saddam Hussein and Al Qaeda terrorists.

More broadly, the 31-page document asserts American dominance as the lone superpower  a status no rival power will be allowed to challenge.

And it provides a reason the world should accept this state of affairs: the expansion of peace and more freedom. A Pax Americana will be "in the service of a balance of power that favors freedom."

Critics are already describing the new strategy as arrogant and dangerous  a far cry from the tone of humility in foreign affairs promised in President Bush's inaugural address. To supporters, it represents an overdue codification of America's mission of global leadership.

"It's a very far-reaching and comprehensive statement, and it's likely to endure as a bedrock element in American thinking in this post cold war world," says Walter Russell Mead, a senior fellow for US foreign policy at the Council on Foreign Relations.

On one thing analysts on both sides agree: In many ways it merely makes explicit what has been US practice for years.

"If you look at our history with Latin America, you could cast much of previous policy as imposing regime changes on the basis that if we don't act, bad things will happen. But to boldly declare such a policy, that's new," says Richard Stoll, professor of political science at Rice University.

Where the Truman-era doctrine of containment had fallen with the Berlin Wall, the Bush document makes a case for preemptive response when there is evidence of an "imminent threat."

At the same time, it details significant new development aid, including a 50 percent rise in US aid to countries that commit to economic freedom and pro-growth policies. The document also proposes a goal of doubling the size of the world's poorest economies within a decade.

When President Truman made the case for a new US strategic doctrine in 1950, the world was still reeling from the carnage of World War II. Communist rivals with the aim of world dominance threatened the peace. A rapid buildup of US military power and presence in strategic areas was needed to contain them, he said.

To Bush and his advisers, the dangers in the post-9/11 world come not from strong states but from weak ones that nurture terrorists with the capacity to create great chaos "for less than it costs to purchase a single tank," the report says.

The first test for this new strategy is Iraq, which the US says poses an immediate threat to world security. The president has also cast the Iraq threat as a test of the credibility of world institutions.

His Sept. 12 speech to the UN General Assembly directed a bright light on how the UN handles enforcement of its own resolutions, and spurred an intense burst of activity to revive enforcement of some 16 Security Council resolutions.

Last week, Iraqi President Saddam Hussein said that he would accept UN weapons inspectors back into the country without conditions.

In New York, US and British diplomats responded by urging a new UN resolution setting a timetable for inspectors to do their work, and specifying consequences if that deadline is not met  as well as other conditions on the search for biological, chemical, or nuclear weapons.

Many members of the UN Security Council say they do not want to take up a military option at this time. And on Saturday, the Iraqi president said that his country would not cooperate with any resolution that is different than those previously voted.

THESE ongoing discussions, including direct talks between President Bush and key leaders, involve some of the most complex and focused diplomatic efforts of the Bush presidency. On Friday, President Bush spoke for half-an-hour with Russian President Vladimir Putin, who favors improved weapons inspection but has not backed use of force. Russia has historic ties to Iraq, as well as billions in outstanding loans.

One usual ally, with whom there has been little discussion, is Germany, where a cabinet official was cited in press reports as comparing President Bush's methods to those of Hitler.

"The Germans won't be able to ask for a permanent seat at the UN [Security Council] for quite some time," says Dominique Moisi, deputy director of the French Institute for International Relations in Paris. France has been moving closer to the US position. He explains that "President Chirac was really alarmed at the level of anti-French bashing in America and [a] priority was to establish a more normal relation with America. Now, we're much closer to America than Germany."

Meanwhile, the Bush administration is taking a similar broad resolution to the US Congress, which is expected to pass authorization to use force before breaking in mid-October.

"The Democrats have been perplexed, maybe even timid as to how they react to the Iraqi crisis," says the former Rep. Lee Hamilton (D) of Indiana, now director of the Woodrow Wilson Center in Washington. "A good many of the Democrats just want to get it off the agenda and get on to other issues before the election."

The end of an era: new threats, new strategies

For us the role of military power is to serve the national purpose by deterring an attack upon us while we seek by other means to create an environment in which our free society can flourish....

Our free society, confronted by a threat to its basic values, naturally will take such action, including the use of military force, as may be required to protect those values.... [Military measures should not be] so excessive or misdirected as to make us enemies of the people....

 1950 Truman administration NSC-68

It has taken almost a decade for us to comprehend the true nature of this new threat. Given the goals of rogue states and terrorists, the United States can no longer rely on a reactive posture as we have in the past. The inability to deter a potential attacker, the immediacy of today's threats, and the magnitude of potential harm that could be caused by our adversaries' choice of weapons, do not permit that option. We cannot let our enemies strike first....

To forestall or prevent such hostile acts by our adversaries, the United States will, if necessary, act preemptively.